Jewelry professionals typically use a handheld monocular, popularly called a loupe, in order to magnify gemstones and other jewelry that they wish to inspect. These loupes have special lenses that allow the viewer's eyes to focus on an object at a much closer distance than is normally possible, making the object appear to be larger and revealing tiny details unseen with normal vision. Loupes are labeled with a number, followed by the symbol “×,” which means “times.” For example, a 2× loupe makes an object appear two times its actual size and a 5× loupe provides a times-five increase.
In other applications, engineers and technicians will use a loupe to inspect a printed circuit board with small surface components on it. Offset printing sees frequent use of loupes in order to carefully analyze how ink lays on paper. Strippers use loupes in order to register film separations to one another. Pressmen use loupes to check registration of colors, estimate dot-gain, and diagnose issues with roller pressure and chemistry based on the shape of individual dots and rosettes. Photographers use loupes to review, edit or analyze negatives and slides on a light table. Many dentists use loupes to better scrutinize the entities within their patients' mouths in order to make a better diagnosis, for example, to determine how far a crack proceeds along the surface of a tooth. Loupes are also used in order to perform on a more precise level; while dentists drill teeth on a millimeter scale, magnification can enlarge the dentists' view of the teeth, perhaps making it easier to inspect teeth for decay and/or see things that ordinarily would not be seen without magnification.
A 10× loupe having a 10× power of magnification is the standard instrument used to determine a diamond's clarity grade in the gemological industry. While higher-power magnification devices may be used to examine the stone, inclusions (internal flaws) and blemishes (surface irregularities) are not factored into the stone's final clarity grade if they are small enough to be undetectable when the stone is examined under 10× magnification. Loupes with black framing around the lens are preferable because black eliminates reflections that can alter the color of the object being viewing.
Loupes made with a single lens are generally of poor quality, distorting the object you're magnifying and adding flashes of color to it. A triplet loupe is a magnifier that contains three lenses placed together in such a way that distortion and color problems are corrected. The distance the loupe is held from an object in order to best the best focus and magnification is the focal length of a loupe and generally decreases as loupe magnification increases. The size of the area viewable through the lens is the field of view. The diameter of the lens affects the field of view as does magnification power—the higher the magnification power the smaller the field of view. The depth of field is related to the distance one can move the loupe towards or away from an item and still have the item in focus. The higher the loupe magnification power, the shorter the depth of field. However, even if these loupe characteristics are optimized, for example in viewing jewelry, without proper illumination, the object being studied will not be clearly visible.
U.S. Pat. No. 4,763,986 discloses an illuminated loupe including a housing having top and bottom covers, a magnifying glass frame pivotally connected between the top and bottom covers and arranged to swing through the covers, a magnifying glass carried by the magnifying glass frame, a light bulb carried by the magnifying glass frame and arranged such that the light therefrom is directed into the frame, and beneath the magnifying glass carried by the frame.
In recent years, semiconductor light emitting diode (“LED”) lamps have come into use in flashlights and other applications. LEDs are typically constructed of gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP) gallium phosphide (GaP), or gallium nitride (GaN). The LED light operates on a low current and a negligible amount of heat is produced. Because of their low level of power required for operation, LEDs have been used to provide illumination for loupes.
U.S. Pat. No. 6,483,651 discloses a magnifying lens apparatus containing a magnifying lens mounted to a support housing. The apparatus contains a light emitting diode lamp to provide at least some illumination to an object being magnified by the magnifying lens.